Landsat: A global land-imaging mission

Since 1972, Landsat satellites have continuously acquired space-based images of the Earth’s land surface, coastal shallows, and coral reefs. The Landsat Program, a joint effort of the U.S. Geological Survey (USGS) and the National Aeronautics and Space Administration (NASA), was established to routinely gather land imagery from space. NASA develops the remotesensing instruments and spacecraft, then launches and validates the performance of the instruments and satellites. The USGS then assumes ownership and operation of the satellites, in addition to managing all ground reception, data archiving, product generation, and distribution. The result of this program is a long-term record of natural and human-induced changes on the global landscape (table 1).

History of the Landsat Program

In the mid-1960s, stimulated by U.S. successes in planetary exploration using unmanned remote-sensing satellites, the Department of the Interior, NASA, and the Department of Agriculture embarked on an ambitious effort to develop and launch the first civilian Earth observation satellite. Their goal was achieved on July 23, 1972, with the launch of Landsat 1, originally named “ERTS” for Earth Resources Technology Satellite. Landsat satellites have since provided worldwide science and resource-management communities with an archive of space-based land remotely sensed data—a valuable resource for people who work in agriculture, geology, forestry, education, regional planning, mapping, and global change research.

Figure 1. Landsat 8 satellite.

The Landsat Data Continuity Mission (LDCM, renamed Landsat 8) (fig. 1), launched on February 11, 2013, joins Landsat 7 (fig. 2) in capturing hundreds of images of the Earth’s surface each day to ensure continuity of data acquisitions to add to the Landsat archive.

The USGS also co-leads the Landsat Science Team that provides technical and scientific input to USGS and NASA to help ensure the success of the Landsat program while providing science support on issues including data acquisition, product access and format, and science and applications opportunities.

Characteristics of the Landsat System

Landsat satellites image the Earth’s surface along the satellite’s ground track in a 185-kilometer-wide (115-mile-wide) swath as the satellite moves in a descending orbit (moving from north to south) over the sunlit side of the Earth.

Landsat 7 and Landsat 8 orbit the Earth at 705 kilometers (438 miles) altitude. They each make a complete orbit every 99 minutes, complete about 14 full orbits each day, and cross every point on Earth once every 16 days. Although each satellite has a 16-day full-Earth-coverage cycle, their orbits are offset to allow 8-day repeat coverage of any Landsat scene area on the globe. Landsat 4 and 5 also followed this orbit. Landsats 1, 2, and 3 orbited at an altitude of 920 kilometers (572 miles), circling the Earth every 103 minutes yielding repeat coverage every 18 days.

The primary sensor onboard Landsats 1, 2, and 3 was the Multispectral Scanner (MSS), with an image resolution of approximately 80 meters in four spectral bands ranging from the visible green to the near-infrared (IR) wavelengths (table 2).

The improved Thematic Mapper (TM) sensors onboard Landsats 4 and 5 were designed with several additional bands in the shortwave infrared (SWIR) part of the spectrum; improved spatial resolution of 30 meters for the visible, near-IR, and SWIR bands; and the addition of a 120-meter thermal-IR band. Landsat 7 carries the Enhanced Thematic Mapper Plus (ETM+), with 30-meter visible, near-IR, and SWIR bands, a 60-meter thermal band, and a 15-meter panchromatic band (table 3).

Improved Data from Landsat 8

Landsat 8 (fig. 1) ensures the continued acquisition and availability of Landsat data, which will be consistent with current standard Landsat data products. About 400 scenes will be acquired each day. All scenes are processed to data products and are available for download within 24 hours of reception and archiving.

Landsat 8 carries two push-broom sensors: the Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS), both of which provide improved signal to noise ratio and 12-bit radiometric quantization of the data.

Figure 2. Landsat 7 satellite.

Figure 3. Landsat 8 Operational Land Imager (OLI) relative spectral response functions.

The OLI collects data in nine shortwave bands—eight spectral bands at 30-meter resolution and one panchromatic band at 15 meters (fig. 3). Refined heritage bands and the addition of a new coastal/aerosol band, as well as a new cirrus band, creates data products with improved radiometric performance. OLI data products have a 16-bit range. A new quality assurance band provides information on the presence of features such as clouds and terrain occlusion.

The TIRS captures data in two long wave thermal bands with 100-meter resolution, and is registered to and delivered with the OLI data as a single product (table 4). TIRS data products have a 30-meter resolution and a 16-bit range.

Applications of Landsat Data

Landsat data are used by government, commercial, industrial, civilian, military, and educational communities throughout the United States and worldwide. The data support a wide range of applications in such areas as global change research, agriculture, forestry, geology, resource management, geography, mapping, water quality, and coastal studies.

Landsat 8 continues the legacy of Landsat missions, while Landsat 7 continues to provide important observations of the Earth, even with the failure of the Scan Line Corrector (SLC) in May 2003.

By March 2013, the network of USGS ground receiving stations had collected nearly 3.7 million Landsat scenes for the U.S. archive. This network, combined with the capabilities of Landsat 7 and Landsat 8 to record and downlink data to foreign sites, enables full coverage of the Earth’s landmasses, although the satellite’s orbit does not include direct over flight of the North or South Pole.

The consistency of Landsat data acquired through the years allows for direct comparison of current specific site images with those taken months, years, or decades earlier. This comparison process can reveal land-cover changes that occur slowly and subtly, or quickly and devastatingly. The richness of the archive, combined with a no cost data policy, allows users to exploit time series of data over extensive geographic areas to establish long-term trends and monitor the rates and characteristics of land surface change. Pre- and post-event Landsat images are invaluable for emergency response and disaster relief. Within hours of data acquisition, the USGS Earth Resources Observation and Science (EROS) Center in Sioux Falls, South Dakota, provides relief organizations worldwide with satellite images for disaster response, as well as image-derived products that incorporate information on population density, elevation, and other environmental factors.

Dam construction and progression of deforestation in Rondônia, Brazil. The image on the left was acquired on June 24, 1984; the right image on August 6, 2011.

Dam construction and progression of deforestation in Rondônia, Brazil. The image on the left was acquired on

August 1985; the right image in September 2010.

Landsat 7 ETM+ —Scan Line Corrector Failure

On May 31, 2003, unusual artifacts began to appear within the data collected by the ETM+ instrument onboard Landsat 7. The problem was caused by failure of the Scan Line Corrector (SLC), which compensates for the forward motion of the satellite to align forward and reverse scans necessary to create an image. Efforts to recover the SLC were unsuccessful. Without an operating SLC, the line of sight traces a zigzag pattern along the satellite ground track with resulting data gaps that form alternating wedges that increase in width from the center of the image to the edge. Landsat 7 is still capable of acquiring highly geometrically and radiometrically accurate data worldwide. The USGS has provided the user community with methods to fill gaps in a Landsat 7 scene. Whether or not they choose to fill the gaps, many users continue to find Landsat 7 data useful.

Information

All Landsat data held in the USGS archives are available for download at no charge and with no user restrictions from EarthExplorer http://earthexplorer.usgs.gov or GloVis http:// glovis.usgs.gov. For information about Landsat operations, technology, and product specifications, visit http://landsat.usgs.gov, or contact:

USGS EROS Landsat Customer Service Mundt Federal Building Sioux Falls, SD 57198 Telephone: 605–594–6151 Fax: 605–594–6589 Email: custserv@usgs.gov

For information about the USGS Land Remote Sensing Program, visit http://remotesensing.usgs.gov.

For additional information about the USGS, visit http://www.usgs.gov or http://ask.usgs.gov.

Where this page came from

This page was imported from U.S. Geological Survey. Published by the U.S. Geological Survey and, as a work of the United States government, in the public domain.

Nobody has written it yet — it is the source material at a new address, which is why search engines are asked to skip it and why no one earns from it. It is up for grabs: take it on, and it is yours to rewrite and to earn from.